1. Field of the Invention
This invention relates to integrated circuits and more particularly to integrated circuits receiving power from a power supply susceptible to noise.
2. Description of the Related Art
In general, integrated circuits receive power from an energy source external to the integrated circuit. The integrated circuit may include a power supply regulation circuit that generates an on-chip, regulated, DC power supply from power received from the external energy source. Typically, the on-chip regulated power supply limits changes in an output voltage or current in response to changes to an external power supply voltage, output load, ambient temperature, time, or other factors. In addition, the on-chip regulated power supply may provide power using a different voltage level (e.g., a voltage level consistent with an on-chip power supply domain) than the voltage level of the external energy source (e.g., a voltage level consistent with an external power supply domain).
A typical output stage of the integrated circuit receives a signal (e.g., a signal consistent with an on-chip power supply domain) from other circuits internal to the integrated circuit and delivers the signal to a terminal (e.g., port, pad, or other suitable output structure) of the integrated circuit. When the output stage is at least partially powered by the external energy source or power supply, the signal delivered to the terminal is susceptible to noise from the external power supply. For example, the signal delivered to the terminal may vary in amplitude or in delay in response to changes to the external power supply voltage.